LindaRN_retired said:

Muscle fiber type changes during GLP-1-mediated weight loss, relevant to lean mass: preliminary biopsy data suggests that weight loss shifts the…

Bone density monitoring on lean mass: DEXA bone density at baseline and month 12.

Lumbar spine T-score: -0.12 → -0.6 (stable to slightly improved)
Femoral neck T-score: -0.11 → -0.7 (stable)

No significant bone loss despite 64 lbs of weight loss. Key factors: adequate calcium (1200mg/day), vitamin D (5000 IU/day), resistance training 3x/week, and adequate protein. Weight-bearing exercise is critical for maintaining bone density during rapid weight loss.

LindaRN_retired said:

Muscle fiber type changes during GLP-1-mediated weight loss, relevant to lean mass: preliminary biopsy data suggests that weight loss shifts the…

Back pain as a lean mass side effect: not from the medication itself, but from rapid body composition changes. Losing 66 lbs shifts your center of gravity and your core muscles need time to adjust.

Physical therapy has been essential. Core strengthening exercises (planks, dead bugs, bird dogs) daily for 10 minutes have eliminated my lower back pain. Your body is literally relearning how to carry itself.

One thing that is still open after LindaRN_retired’s answer:

What would you measure differently if you were starting again?

hank_denver said:

Back pain as a lean mass side effect: not from the medication itself, but from rapid body composition changes.

Pushing back on hank_denver here. I think the framing smuggles in the conclusion. Ask it the other way round and the obvious answer reverses, which usually means the question is doing the work.

hank_denver said:

Back pain as a lean mass side effect: not from the medication itself, but from rapid body composition changes.

Correct as far as it goes. The part it does not cover is what to do when the honest answer is "not enough data", which is more often than anyone likes.